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: Interest in the L12 phase in the Al-Ti-Cr system has increased with respect to the demand for light weight materials at elevated temperature because of its enhanced mechanical properties that arise through the substitution of Cr for Al in Al3Ti intermetallic compounds. Additionally, recent work has indicated that the application of L12- based alloys was extended to oxidation resistance coating materials for γ-based TiAl alloy because the L12 phase could form a protective Al2O3 scale under oxidizing environments. However, L12 phase decomposes partially or completely to a more brittle phase when exposed to temperatures in the range of 800~1000o C, resulting a serious degradation of the cracking resistance in L12-based alloys. In this study, Zr was substituted for Ti in Al-21Ti-23Cr alloys to improve the phase stability around 800o C. As a result of Zr addition in L12-based Al-Ti-Cr alloys, the fraction of L12 phase decomposition at 800o C was decreased. Furthermore, temperature range, in which L12 phase was decomposed to other brittle phase, was shrunken when Zr was added in the Al-Ti-Cr alloys. These phenomena resulted from the fact that the L12 phase field was less shifted in the direction of the Al-rich corner at 800o C in the Al-Ti-Cr system and that atomic diffusion for the L12 phase decomposition was reduced. Therefore, the addition of Zr is required to increase the possibility for potential usage of L12-based Al-Ti-Cr alloys at elevated temperatures around 800o C because of the improvement of phase stability